Magnetron



Sept. 30, 1947.

J. P. BLEWVETT MAGNETRON Filed Sept. 23, 1944 2 Sheets-Sheet 1 Ihventor; John P Bleweot Hus Attorney.

Sept. 30, 1947. BYLEWETT 2,428,193

- I MAGNETRON Fi led Sept. 25, 1944 2 She'ets-Sheet 2 I, II I,

' vento Jo F. Blew "0,

His Attorney.

Patented Sept. 30, 1947 UNITED STATES PATENT OFFICE John P. Blewett, Schenectady, N. assignor to General Electric Company, a corporation ofi New York Application September 23, 1944. septum-555397 2 Claims. (01. 315-39) My invention relates to electric discharge de-.

provide an improved magnetron construction of this general type which offers numerous advantages from the standpoint of manufacture, ad justment of the frequency of oscillation, cooling of the electrodes, and maximum power output.

It is an object. of my invention to provide a new and improved electric discharge device of the magnetron type; i

It is another object of my invention to provide a new and improved anode structure and associated' high frequency conductors which facilitates manufacture of the magnetron.

It is a still further object of my invention to provide a new and improved magnetron construction. which provides a simple structure for the fluid cooling of the anode elements and permits operation of the tube at high power outputs.

. In one illustrated embodiment of myinvention, the anode structure includes a pair of anode ele-v merits having generally semi-cylindrical surfaces arranged on opposite sides of an elongated cathode member to define a substantially cylindrical or annular inter-electrode space. The anode members have their opposed ends spaced to provide gaps. The electrode assembly of which the anode members are a part includes a generally U-shaped structure of hollow tubing, Preferably of good conducting material such as cop-per. The U-shaped assembly is mounted within a dielectric envelope with the parallel arms extending through one end of the envelope and providing connections for a high frequency transmission line. The closed portion of the U-sha-ped structure extends within the envelope and provides atransmission line section which cooperates with the exterior transmission line to determine the operating frequency of the device.

For a better understanding of my invention,

reference may be had to the following descrip- V t'ion taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims. In the drawings Fig. 1 is a perspective view. of one embodiment of my invention; Fig. 2 is an elevational view of a portion of the embodiment illustrated in Fig. 1; Fig. 3 is an elevational View, partially in section, of a modifled form of my invention, and Fig. 4 is a plan ,minals for a, source of heating current.

. 2 view in section of the embodiment, illustrated in Fig. 3.

Referring now to Fig. I of the drawings, I have shown my invention embodied in a mag,- netron, device including an. elongated glass envelope I of generally cylindrical form. The envelope encloses an anode structure comprising two. anode members. 2 and .3 havingsemi-cylindrical facesarranged in opposed relation to pro-- vide acircular array- As illustrated in the drawi-ngs... the members 2: and, 3 are. mounted in mu;- tually spaced relation to provide. gaps 6 and 5 between them and are respectively supported by parallel conductors B and 't' which extend through one end of the envelope and. are sealed thereto in any suitable manner. A generally U-shapedloop conductor 8, lying within the envelope,; interconnects the. anode; members 2: and 3;. The con.- ductors 6; 1 and 8 are preferably-v of hollow conductingv tubing so that in addition to providinghigh frequency-connections with the anode. niern hers 2. and 3: they provide. a closed circuit for the flow; of cooling fluid. To this end, suitable passages (not shown) are provided through anode members 2 and 3 and the ends of'conductors 6, l and 8 are positioned in these passagesv and secured in vacuum-tight. relation with respect to the. anode members in any suitable manner, as bysilver soldering.

.A source ofelectrons in the generally annular space defined by the: members 2. and- 3 is pro.- vided by an elongated cathode 9' which may be a tungsten wire, either uncoatedor coated with a suitable oxide. The cathode is supported symmetrically between the curved; surfaces of the anode. members. Z and: 3: by lead-in conductors; l0 and H- which are sealed through the base of envelope, I. to provide, externally accessible ter- One of the terminals may also be connected to a source of high negative direct current voltage if the anodeis to be, operated. at ground potential. It, is preferable to provide a spring mounting for the cathode such as provided by the spring arm 12; supported byconductor lllas shown in Fig.1 2,. Suitable end plates: or shields. l3, supported from conductor H' by a wire bracket l4, are provided to minimize the escape of electrons from the inter-electrode space.

In Fig. 1 is shown a magnetron device embodying the present invention supported on a metallic shielding enclosure [5 ofv generally rectangu la'r shape. The top and front sides of the enclosurehave'. been removed to show the high.

frequency conductors andv tuning arrangement associated with the anode conductors 6 and 1. As illustrated in Fig, 1, the output circuit of the device includes tubular conductors l6 and H which form extensions of conductors 6 and I. The conductors l6 and I! are of larger internal diameter than conductors 6 and 1 and are provided with resilient end portions l8 which engage enlarged shoulders or terminals l9 prow'dedon the conductors 6 and 1 in the region where those conductors are sealed through the envelope. A

funnel-like adapter 20 is provided on the interior of each of the conductors I6 and I1 and together with the resilient sleeve 2! provides means for making a detachable fluid-tight connection between conductors I5 and IT and 6 and 1', respec-'- tively. In this manner cooling fluid, such as air,

; is similar in many respects to the modification of oil or water, may be circulated from one conduc- I tor 16 through conductors B, 1 and 8 and the anode members 2 and 3 to the other conductor H.

The operating frequency of the magnetron device is determined by the electrical characteristics of the anode circuit including the anode members 2 and 3, loop conductors 6, 1 and 8 and the effective length of conductors l6 and I1. Provision is made for adjusting the operating frequency of the device by an adjustable metallic plate 22 which is shaped to engage the inner walls of the shielding enclosure [5 and conductively to engage both of the conductors l6 and H. The position of the member 22 is adjusted by moving the operating rod 22' with any suitable adjusting mechanism (not shown). -As illustrated in the drawings, the edges of the member 22 are provided with resilient fingers 23 which engage the wall of the shielding enclosure. It will b understood that'similar resilient fingers may be provided to engage the conductors l6 and [1. High frequency energy may be delivered to an output circuit in any suitable manner and in the arrangement illustrated in Fig. 1 a suitable conductive connection including contact 24 is provided. This contact is mounted in insulated relation with respect to the shielding enclosure l5 by means including a fastening element 25 and a pair of insulating washers 2B, The conductor 24 is arranged to slide in a slot 27 provided in one wall of the enclosure [5. If desired, movement of the contact 24 may be accomplished by coupling to the mechanism for moving the contacting member 22. Contact 24 may be connected to the central conductor of a concentric output transmission line (not shown).

As is well understood by those skilled in the art, in magnetron devices of the type described above it is necessary to produce a magnetic field in the inter-electrode space which is substantially parallel to the elongated cathode member. In Fig. 2 there is illustrated schematically a pair of pole pieces 28 of an electromagnet (not shown).

The general rinciples of operation of magnetron devices of the type described above in connection with Figs. 1 and 2 is believed to be well understood by those skilled in the art. With a suitable unidirectional voltage impressed between the anode members and cathode and with a suitable magnetic field established in the interelectrode space, electrons emitted by cathode 9 move in the inter-electrode space in curvilinear paths due to the resultant action of the electric and magnetic fields and excite the anode structure at a frequency determined by the geometry of the anode structure and the circuits associated therewith. With the .particular arrangement illustrated, the frequency of the oscillati ns Figs. 1 and 2 and is particularly adapted for high power continuous wave operation. Referring now to Fig. 3, the magnetron device there illustrated comprises a metallic envelope 29 of generally cylindrical shape having a cover member 30 provided with an integral upstanding flange 3| for the urpose of supporting a cathode assembly. The cathodeassembly, as illustrated, includes a spool-like cathode member 32 preferably formed of a material such as beryllium copper coated with a good secondary emitter such as magnesium or Dow metal. The cathode member 32 is provided with a recess 33 which houses a small filamentarycathode 34 for providing a source of primary electrons. The filamentary cathode 34 has one terminal thereof connected with the cathode member 32 and the other terminal connected with an externally accessible insulated conductor 35. 'The entire cathode assembly is supported from the flange 3| in insulated relation with respect to the envelope 29 by a tubular member of conducting material 35 which extends upwardly through the flange 3| and is secured to a suitable metallic sleeve 36 which is, in turn, supported in insulated relation with respect to flange 3| by a glass sleeve 31. The cathode assembly may be made removable and be held in position within the sleeves 3i and 36 by'a closure member 38 which is threaded, or otherwise secured, to the upper end of the sleeve 36. Suitable pipes 39 and 40 may be provided in the cathode assembly for supplying cooling fluid to the interior of the main cathode body- 32. The cathode structure described above is claimed and more fully described in the copending Blewett and Langmuir application, Serial No.

555,496, filed concurrentl herewith and assigned to the assignee of the present application.

The anode structure of the modification shownin Figs. 3 and 4 is in general similar to that shown in Figs. 1 and 2 and comprises a pair of anode members 4| and 42 which are arranged on opposite sides of the cathode member 32 and shaped to provide a generally annular inter-electrode space. The members 4i and 42 ar mutually spaced to provide gaps 43 and 44. Hollow tubular conductors 45, 46, and 41, 48 are connected with the opposite ends of anode members 4| and 42 and extend through the side wall of the container 29 to support the anode members 4| and 42. on the exterior of the container 29 by a fitting 49 to complete a circuit for the flow of cooling fluid from conductor 46 to conductor 48. When employing a metallic container, such as illustrated by container 29, the effective length of the loop including conductors 45 and 48 is determined by the wall of container 29 rather than by the end of the loop provided by member 49. In the arrangement illustrated a conducting member 50 is arranged to engage the conductor 46 and to be moved along the length of these conductors by a suitable adjusting screw 5! to;

Conductors 45 and 41 are preferably joined.

adjust the operating frequency of the device. The mechanical connection between the operating screw 5! and the conductor 5!] may be made through the housing in any suitable manner, and preferably is madethrough a bellows 52 to permit movement of the member 50 while the container 29 remains adequately sealed. High frequency energy ma be extracted from the anode system of the device in any suitable manner. As illustrated in Fig. 4 of the drawings, the internal conductor 53 of a concentric-type transmission line is conductively connected with the conductor 45, The conductor 53 is preferably hollow and connected into the hollow conductor 45 so that cooling fluid may be circulated through the conductor 53 by the same cooling system as employed for the remainder of the device. The conductor 53 is supported in insulated relation with respect to the container 29 and the outer conductor 59 of the output transmission line by an insulating disk 55. In Fig. 3 fragmentary portions of the electromagnetic pole pieces have been illustrated at 56.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope 'of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A magnetron device including an hermetically sealed envelope, a structure for generating oscillations comprising a U-shaped conductive member of hollow tubing having a U-shaped end thereof within said envelope and parallel arms thereof extending through a wall of said envelope, said arms constituting a high frequency transmission line and said U-shaped end constituting a section determining the operating frequency of said structure, a conductor exterior of said envelope connecting said arms further determining the operating frequency of said structure, a pair of anode members within said envelope each supported by one of said arms intermediate said U-shaped end and said exterior conductor, said anode members having opposed curved surfaces defining a substantially cylindrical space, and a cathode within said space for supplying electrons thereto.

2. A magnetron device including an hermetically sealed envelope, a structure for generating oscillations comprising a U-shaped conductive member of hollow tubing adapted to close a circuit for the flow of cooling fluid and having a U-shaped end thereof within said envelope and parallel arms thereof extending through a wall of said envelope, said arms constituting a high frequency transmission line and said U-shaped end constituting a section determining the operating frequency of said structure, a conductor exterior of said envelope connecting said arms and adjustably positionable longitudinally thereof for further determining the operating frequency of said structure, a pair of anode members within said envelope each supported by one of said arms intermediate said U-shaped end and said exterior conductor, said anode members having opposed curved surfaces defining a cylindrical space charge chamber, and a cathode coaxially mounted within said chamber for supplying electrons thereto.

JOHN P. BLEWE-TT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,189,501 Helbig Feb. 6, 1940 2,023,272 Hulster Dec. 3, 1935 2,145,735 Rice Jan. 31, 1939 2,216,169 George et al Oct. 1, 1940 2,295,396 George Sept. 8, 1942 2,114,114 Van B. Roberts Apr. 12, 1938 1,562,172 Housekeeper Nov. 1'7, 1925 FOREIGN PATENTS Number Country Date 509,102 Great Britain .2. Sept. 11, 1939 443,077 Great Britain Feb. 20, 1936 

